Belfast city, London city, Dublin (US Immigration on site is a godsend but have seen 90 min queues) Leeds Bradford, Edinburgh and Stansted all decent local airports, Laguardia, Aberdeen, East Midlands, Luton (barring heavy refurbs a few years before lockdown), Colombo (we got an armed guard from the plane) never really had any bad experiences, security usually fine to get through quickly and cover basics ok.
Changi, Shanghai Pudong, Paris CDG, Indira Gandhi, Copenhagen were all enjoyable enough with no big negatives each have their quirks but mainly good to travel through.
Pune, Manchester, Belfast Int, Gatwick and Cleveland Hopkins all almost as bad as eachother for various reasons from understaffed, slow security, unjustifiably high food prices to absolute lack of hygiene and or insects.
JFK, Dubai, Boston Logan, Birmingham and Heathrow were all just slogs to the gates at times and were never much fun. The A380 top deck out of Dubai was a great experience though, not quite 1st class seats but staff, food and facilities were top notch.
Edit: isn't that just anawful wall of text.